The present invention relates to a nanoporous film and fabrication method thereof, and more particularly to a nanoporous film with superior mechanical strength and anti-reflectivity.
Antireflection film is generally disposed on an outermost surface of an image display device such as optical lens, cathode ray tube display device (CRT), plasma display panel (PDP), liquid crystal display device (LCD), or organic electroluminescent device, to reduce reflectance so as to prevent optical interference from external light.
Single-layer antireflection film provides high yield, simple fabrication process, and low cost, making them a popular display industry choice. Antireflection film of conventional organic compounds containing fluorine used in multi-layer antireflection films, such as CaF2, or MgF2, cannot, however, achieve sufficiently high scratch resistance due to the poor cohesion of fluorine-containing compounds. Thus, a hard coat layer is formed thereon. Furthermore, the antireflection film made thereby has a sufficient refractive index of only 520 to 570 nm, and refractive index thereof cannot be further reduced to 1.40 or less.
A conventional single-layer antireflection film with a wave-shaped profile has been disclosed, providing lower refractive index, with fabrication thereof comprising a blend of tetramethoxysilane (TMOS) and a mutually incompatible polymer dissolved in a solvent to provide a solution with a common intermixed phase, and a substrate coated with the solution. After curing the coating, the TMOS undergoes a cross-link reaction to form TMOS condensation. Finally, the mutually incompatible polymer is removed from the coating, forming an antireflection film with a wave-shaped profile. Since the antireflection film has a plurality of vertical openings of differing depths, the antireflection film has a gradient refractive index, further obtaining a low reflectance. The antireflection film consists of the TMOS condensation, with scratch resistance of the antireflection film depending on bond strength thereof, i.e. bond strength of Si—O—Si bonds. Due to the low cross-link density of the TMOS condensation, the antireflection film, however, exhibits inferior mechanical strength and scratch resistance failing to meet the demands of the flat panel display industry.
Therefore, it is necessary to develop an antireflection film with low refractive index and high mechanical strength.